I bought a S&W M&P 15 in 5.56 and wanted to ask about what other uppers would fit on this gun? The reason for asking is that the 5.56 ammo is getting hard to find and is pricier than .223. If I would buy a less popular caliber that costs even a little more I will be able to find ammo more readily available.

I already have a M&P 15-22 so I don't need a .22. What is out there that won't make the ammo too much but more available?

Lots of different caliber uppers will fit but in general, ammo wise, they all cost a lot more than .223, with the exception of 5.45x39. I'd stick with 5.56/.223.

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The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together.
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US Army 1966-69, VFW Life Member, Retired Geek

The 5.56 is proving hard to find this week. I like to put in a good stockpile of ammo for all the calibers I own. I bought 140 .223 on Friday at $7.75/20. The same brand in 5.56 would have been 11.95/20. Why the difference? How is the .223 going to shoot in the 5.56 chamber?

The 5.56 is proving hard to find this week. I like to put in a good stockpile of ammo for all the calibers I own. I bought 140 .223 on Friday at $7.75/20. The same brand in 5.56 would have been 11.95/20. Why the difference? How is the .223 going to shoot in the 5.56 chamber?

The .223 will shoot just fine out of a 5.56 chamber , basically the same cartridge just lesser pressure , I shoot .223 ammo out of all my 5.56 barrels and it works just fine

Don't buy the tracer, or at least be careful with it. It can start fires and no rifle should get a steady diet of it.

__________________
______
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together.
________________________________________
US Army 1966-69, VFW Life Member, Retired Geek